1. Field of the Invention
The present invention relates to a motor driving device of a camera, and more particularly to a motor driving device comprising a control device which is able to accurately control the motor driving amount.
2. Description of the Prior Art
There are known cameras in which a camera load such as film winding is operated by an electric film winding motor. In cameras of the above-mentioned type, it is also known to provide an instruction signal output device which is operable with a film winding mechanism for outputting an instruction signal to continue the film winding operation, so that when the instruction signal disappears, the film winding up operation is stopped by causing the film winding motor to be braked.
The control mechanism of the type mentioned above is conventionally provided with one or more circular electrodes which are partially cut, and an electric brush arrangement linked with the film winding mechanism is adapted to be moved along the electrode, whereby when one frame of the photographic film is advanced, the film winding motor is braked and stopped by detecting that the brush reaches the cut portion of the electrode.
In the camera mentioned above, if a wide range of power source voltages is available to drive the film winding motor, the difference in the amount of the movement of the photographic film after the film winding motor is braked varies largely, in dependence on whether the film winding motor is driven by the maximum voltage in the range or by the minimum voltage, even if the motor is braked for the same time. In the case of winding the photographic film by the film winding motor, for example, when it is so designed that the regular interval between two adjacent frames is not so large for when the maximum power source voltage is present, if the power source voltage is then decreased to the minimum voltage in the range, since the inertial energy of the film winding motor is smaller than the inertial energy of the film winding motor driven by the maximum voltage, when the brush reaches the cut portion of the electrode and the film winding motor is braked, the film winding motor is stopped rapidly and the frame advance with the regular interval can not be performed. Moreover, in the extreme case, there may occur a problem of a shortening of the film advance, whereby the preceding frame and the next adjacent frame are overlapped.